The present invention relates, in general, to a projector including a discharge lamp as a light source to project and display an image and, in particular, to a cooling mechanism for a projector for suitably cooling a light source lamp.
Projectors focuses light emitted from a light source with a reflector, lens, and other parts, let the focused light pass through a display element, such as a liquid crystal panel, to form an optical image, and project the optical image onto, for example, an external screen via a projection lens or a projection mirror. A discharge lamp, such as a high-pressure mercury lamp, is typically used as the light source for the projector. The discharge lamp is substantially hermetically sealed by a reflector on the back and an explosion-proof glass at the front. The discharge lamp tends to become hot when turned ON and is thus designed to be operated at a predetermined appropriate temperature. If the discharge lamp is continuously used at a temperature exceeding the appropriate one, a reduced lamp life could result, or the lamp may explode or fail to turn ON. To prevent the foregoing from happening, the projector typically includes a cooling mechanism that uses a fan for performing forced cooling in order to keep the discharge lamp at the appropriate temperature. An upper portion of a light emitting section, in particular, of the discharge lamp used in the projector tends to become hot, so that the upper portion is specifically cooled to thereby even out temperatures throughout the discharge lamp and maintain the appropriate temperature.
In general, the projector is mounted horizontally on a desk or suspended from a ceiling. When mounted on the desk, the projector very often projects obliquely upwardly. If the projector is mounted on the ceiling in an identical attitude as that when mounted on the desk, the projector projects toward the ceiling. Accordingly, the projector is turned upside down when mounted on the ceiling to thereby project obliquely downwardly. In this case, the discharge lamp inside the projector is also turned upside down. The lamp cooling mechanism is therefore required to maintain the appropriate temperature (temperature distribution) at all times, regardless of whether the projector is mounted on the desk or the ceiling.
A technique disclosed in JP-A-10-106307, for example, is known as one for cooling the discharge lamp of the projector. In the technique disclosed in JP-A-10-106307, a lamp housing for supporting a discharge lamp has opening portions for cooling the lamp at upper and lower portions of one side thereof. The lamp housing further includes a shutter that selects an opening area of the opening portions. The shutter vertically slides to select the opening area according to an attitude of the lamp housing mounted for application. This allows air from a cooling fan to be directed toward the upper portion of the lamp housing, even if the lamp housing is mounted in an upside down attitude.